1. Field of the Invention
The present invention relates to a lever switch mounted on a steering column of an automobile vehicle such as a car, in particular to the lever switch having a contact assembly including a movable contact piece and a fixed contact piece.
2. Related Art
A car has a lever switch generally mounted on a steering column for operation of various equipment including lighting devices, wipers, turn signal lamps, and so on.
Furthermore, the lever switch has an adjustment device for adjusting a force to turn the operating body and has a push device for resiliently urging the movable contact piece toward the fixed contact piece for electrical connection thereof. Each of the adjustment device and the push device has a spring as a resiliently urging means. Each spring has a relatively strong resilient force to bias the movable contact piece directly or through the operating body toward the fixed contact piece.
For example, Japanese Patent Application Laid-open NO. H. 10-233144 discloses a lever switch having a movable contact piece that is a roller rolling on a fixed contact piece. The roller is resiliently urged by a push device consisting of a coil spring toward the fixed contact piece.
The conventional lever switch has a adjustment device for the turning force of the operating body. The turning of the operating body around the shaft causes the coil spring of the adjustment device to adjust the force resiliently exerted on the movable contact piece toward the fixed contact piece. Thereby, in response to the turning of the operating body, the force abutting the movable contact piece against the fixed contact piece is variable. This may not provide a stable constant contact force between the movable contact piece and the fixed contact piece.
Furthermore, an incorrect electrical connection between the movable contact piece and the fixed contact piece may occur due to a with-time degradation of at least one of the movable contact piece and the fixed contact piece. The degradation is caused by the repeated turning of the operating body, the variation of the force abutting the movable contact piece against the fixed contact piece, and the resilient force of the coil springs of the adjustment device and the resiliently pushing device.
In view of the disadvantages of the conventional lever switch, an object of the present invention is to provide a lever switch having a contact assembly to ensure a stable correct electrical connection between a movable contact piece and a fixed contact piece.
For achieving the object, a lever switch according to the present invention has a shaft, an operating body turnable around the shaft, and a contact assembly. The contact assembly includes a movable contact piece turning in response to the turn of the operating body, a fixed contact piece secured to the shaft and slidingly contacting the movable contact piece, and a movable contact piece retainer disposed between the operating body and the fixed contact piece for retaining the movable contact piece. The movable contact piece retainer is opposed to the operating body and the fixed contact piece in the longitudinal direction of the shaft. A first clearance is provided between the movable contact piece retainer and the fixed contact piece in the longitudinal direction of the shaft, and a second clearance is provided between the movable contact piece retainer and the operating body in the longitudinal direction of the shaft.
As described above, the movable contact piece retainer is disposed between the fixed contact piece and the operating body with the clearances therebetween. Thus, the push force exerted on the fixed contact piece by the operating body through the movable contact piece retainer is adjusted by the clearances. Hence, the contact force provided between the movable contact piece and the fixed contact piece is adjusted in variation thereof.
Preferably, the movable contact piece retainer is formed in a circular ring shape. A fixed body is secured to the shaft and positioned adjacent to an inner periphery of the movable contact piece retainer, the fixed body being axially opposed to the operating body. A resiliently urging means is mounted between the fixed body and the operating body to resiliently bias the operating body in the direction opposed to the fixed body. A third clearance is provided between the fixed body and the operating body. The third clearance is smaller than the second clearance.
Thus, on turning the operating body, the operating body does not abut against the movable contact piece retainer, even when the operating body makes contact with the fixed body, that is, with the fixed contact piece against the resilient force of the resiliently urging means. That is because the third clearance is smaller than the second clearance.
This retards a force abutting the movable contact piece against the fixed contact piece, when the turning of the operating body moves the movable contact piece toward the fixed contact piece via the movable contact piece retainer.
Preferably, the resiliently urging means is axially positioned in a recess of the operating body, and the fixed body is formed in a cylindrical shape. The fixed body has a cam end wall opposed to the operating body. The cam end wall is inclined in axial and circumferential radial directions of the fixed body. The cam end wall abuts against a rolling body resiliently urged by the resiliently urging means toward the fixed body such that the rolling body can roll on the cam end wall.
Thus, the rolling body rolling on the cam wall moves the operating body in a direction opposed to the fixed body via the resiliently urging means.
The operating body may be formed with a first projection and a first depression which are opposed to the movable contact piece retainer at one end of the operating body, while the movable contact piece retainer is formed with a second projection and a second depression which are opposed to the operating body at one end of the movable contact piece retainer. The first projection engages with the second depression and the second projection engages with the first depression so that the operating body can turns around the shaft together with the movable contact piece retainer.
Thus, the turning of the operating body surely turns the movable contact piece via the movable contact piece retainer.
Preferably, the movable contact piece makes contact with the fixed contact piece, and the movable contact piece is a flat spring resiliently urging the movable contact piece retainer in a direction opposed to the fixed contact piece.
This further retards a force abutting the movable contact piece against the fixed contact piece, when the turning of the operating body moves the movable contact piece toward the fixed contact piece via the movable contact piece retainer.